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/* |
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* Written by Doug Lea with assistance from members of JCP JSR-166 |
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* Expert Group and released to the public domain, as explained at |
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* http://creativecommons.org/publicdomain/zero/1.0/ |
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*/ |
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|
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package java.util.concurrent; |
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|
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import java.io.ObjectStreamField; |
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import java.util.Random; |
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import java.util.Spliterator; |
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import java.util.concurrent.atomic.AtomicInteger; |
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import java.util.concurrent.atomic.AtomicLong; |
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import java.util.function.DoubleConsumer; |
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import java.util.function.IntConsumer; |
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import java.util.function.LongConsumer; |
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import java.util.stream.DoubleStream; |
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import java.util.stream.IntStream; |
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import java.util.stream.LongStream; |
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import java.util.stream.StreamSupport; |
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|
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/** |
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* A random number generator isolated to the current thread. Like the |
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* global {@link java.util.Random} generator used by the {@link |
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* java.lang.Math} class, a {@code ThreadLocalRandom} is initialized |
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* with an internally generated seed that may not otherwise be |
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* modified. When applicable, use of {@code ThreadLocalRandom} rather |
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* than shared {@code Random} objects in concurrent programs will |
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* typically encounter much less overhead and contention. Use of |
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* {@code ThreadLocalRandom} is particularly appropriate when multiple |
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* tasks (for example, each a {@link ForkJoinTask}) use random numbers |
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* in parallel in thread pools. |
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* |
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* <p>Usages of this class should typically be of the form: |
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* {@code ThreadLocalRandom.current().nextX(...)} (where |
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* {@code X} is {@code Int}, {@code Long}, etc). |
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* When all usages are of this form, it is never possible to |
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* accidently share a {@code ThreadLocalRandom} across multiple threads. |
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* |
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* <p>This class also provides additional commonly used bounded random |
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* generation methods. |
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* |
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* @since 1.7 |
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* @author Doug Lea |
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*/ |
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public class ThreadLocalRandom extends Random { |
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/* |
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* This class implements the java.util.Random API (and subclasses |
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* Random) using a single static instance that accesses random |
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* number state held in class Thread (primarily, field |
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* threadLocalRandomSeed). In doing so, it also provides a home |
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* for managing package-private utilities that rely on exactly the |
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* same state as needed to maintain the ThreadLocalRandom |
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* instances. We leverage the need for an initialization flag |
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* field to also use it as a "probe" -- a self-adjusting thread |
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* hash used for contention avoidance, as well as a secondary |
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* simpler (xorShift) random seed that is conservatively used to |
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* avoid otherwise surprising users by hijacking the |
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* ThreadLocalRandom sequence. The dual use is a marriage of |
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* convenience, but is a simple and efficient way of reducing |
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* application-level overhead and footprint of most concurrent |
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* programs. |
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* |
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* Even though this class subclasses java.util.Random, it uses the |
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* same basic algorithm as java.util.SplittableRandom. (See its |
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* internal documentation for explanations, which are not repeated |
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* here.) Because ThreadLocalRandoms are not splittable |
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* though, we use only a single 64bit gamma. |
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* |
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* Because this class is in a different package than class Thread, |
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* field access methods use Unsafe to bypass access control rules. |
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* To conform to the requirements of the Random superclass |
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* constructor, the common static ThreadLocalRandom maintains an |
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* "initialized" field for the sake of rejecting user calls to |
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* setSeed while still allowing a call from constructor. Note |
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* that serialization is completely unnecessary because there is |
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* only a static singleton. But we generate a serial form |
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* containing "rnd" and "initialized" fields to ensure |
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* compatibility across versions. |
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* |
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* Implementations of non-core methods are mostly the same as in |
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* SplittableRandom, that were in part derived from a previous |
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* version of this class. |
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* |
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* The nextLocalGaussian ThreadLocal supports the very rarely used |
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* nextGaussian method by providing a holder for the second of a |
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* pair of them. As is true for the base class version of this |
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* method, this time/space tradeoff is probably never worthwhile, |
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* but we provide identical statistical properties. |
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*/ |
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|
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/** Generates per-thread initialization/probe field */ |
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private static final AtomicInteger probeGenerator = |
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new AtomicInteger(); |
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|
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/** |
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* The next seed for default constructors. |
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*/ |
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private static final AtomicLong seedGenerator = |
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new AtomicLong(mix64(System.currentTimeMillis()) ^ |
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mix64(System.nanoTime())); |
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|
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/** |
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* The seed increment |
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*/ |
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private static final long GAMMA = 0x9e3779b97f4a7c15L; |
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|
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/** |
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* The increment for generating probe values |
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*/ |
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private static final int PROBE_INCREMENT = 0x9e3779b9; |
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|
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/** |
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* The increment of seedGenerator per new instance |
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*/ |
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private static final long SEEDER_INCREMENT = 0xbb67ae8584caa73bL; |
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|
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// Constants from SplittableRandom |
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private static final double DOUBLE_UNIT = 1.0 / (1L << 53); |
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private static final float FLOAT_UNIT = 1.0f / (1 << 24); |
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|
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/** Rarely-used holder for the second of a pair of Gaussians */ |
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private static final ThreadLocal<Double> nextLocalGaussian = |
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new ThreadLocal<Double>(); |
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|
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private static long mix64(long z) { |
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z = (z ^ (z >>> 33)) * 0xff51afd7ed558ccdL; |
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z = (z ^ (z >>> 33)) * 0xc4ceb9fe1a85ec53L; |
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return z ^ (z >>> 33); |
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} |
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|
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private static int mix32(long z) { |
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z = (z ^ (z >>> 33)) * 0xff51afd7ed558ccdL; |
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return (int)(((z ^ (z >>> 33)) * 0xc4ceb9fe1a85ec53L) >>> 32); |
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} |
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|
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/** |
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* Field used only during singleton initialization. |
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* True when constructor completes. |
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*/ |
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boolean initialized; |
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|
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/** Constructor used only for static singleton */ |
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private ThreadLocalRandom() { |
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initialized = true; // false during super() call |
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} |
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|
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/** The common ThreadLocalRandom */ |
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static final ThreadLocalRandom instance = new ThreadLocalRandom(); |
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|
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/** |
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* Initialize Thread fields for the current thread. Called only |
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* when Thread.threadLocalRandomProbe is zero, indicating that a |
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* thread local seed value needs to be generated. Note that even |
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* though the initialization is purely thread-local, we need to |
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* rely on (static) atomic generators to initialize the values. |
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*/ |
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static final void localInit() { |
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int p = probeGenerator.addAndGet(PROBE_INCREMENT); |
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int probe = (p == 0) ? 1 : p; // skip 0 |
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long seed = mix64(seedGenerator.getAndAdd(SEEDER_INCREMENT)); |
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Thread t = Thread.currentThread(); |
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UNSAFE.putLong(t, SEED, seed); |
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UNSAFE.putInt(t, PROBE, probe); |
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} |
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|
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/** |
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* Returns the current thread's {@code ThreadLocalRandom}. |
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* |
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* @return the current thread's {@code ThreadLocalRandom} |
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*/ |
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public static ThreadLocalRandom current() { |
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if (UNSAFE.getInt(Thread.currentThread(), PROBE) == 0) |
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localInit(); |
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return instance; |
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} |
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|
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/** |
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* Throws {@code UnsupportedOperationException}. Setting seeds in |
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* this generator is not supported. |
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* |
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* @throws UnsupportedOperationException always |
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*/ |
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public void setSeed(long seed) { |
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// only allow call from super() constructor |
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if (initialized) |
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throw new UnsupportedOperationException(); |
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} |
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|
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final long nextSeed() { |
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Thread t; long r; // read and update per-thread seed |
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UNSAFE.putLong(t = Thread.currentThread(), SEED, |
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r = UNSAFE.getLong(t, SEED) + GAMMA); |
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return r; |
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} |
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|
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// We must define this, but never use it. |
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protected int next(int bits) { |
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return (int)(mix64(nextSeed()) >>> (64 - bits)); |
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} |
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|
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// IllegalArgumentException messages |
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static final String BadBound = "bound must be positive"; |
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static final String BadRange = "bound must be greater than origin"; |
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static final String BadSize = "size must be non-negative"; |
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|
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/** |
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* The form of nextLong used by LongStream Spliterators. If |
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* origin is greater than bound, acts as unbounded form of |
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* nextLong, else as bounded form. |
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* |
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* @param origin the least value, unless greater than bound |
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* @param bound the upper bound (exclusive), must not equal origin |
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* @return a pseudorandom value |
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*/ |
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final long internalNextLong(long origin, long bound) { |
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long r = mix64(nextSeed()); |
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if (origin < bound) { |
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long n = bound - origin, m = n - 1; |
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if ((n & m) == 0L) // power of two |
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r = (r & m) + origin; |
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else if (n > 0L) { // reject over-represented candidates |
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for (long u = r >>> 1; // ensure nonnegative |
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u + m - (r = u % n) < 0L; // rejection check |
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u = mix64(nextSeed()) >>> 1) // retry |
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; |
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r += origin; |
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} |
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else { // range not representable as long |
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while (r < origin || r >= bound) |
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r = mix64(nextSeed()); |
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} |
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} |
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return r; |
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} |
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|
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/** |
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* The form of nextInt used by IntStream Spliterators. |
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* Exactly the same as long version, except for types. |
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* |
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* @param origin the least value, unless greater than bound |
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* @param bound the upper bound (exclusive), must not equal origin |
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* @return a pseudorandom value |
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*/ |
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final int internalNextInt(int origin, int bound) { |
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int r = mix32(nextSeed()); |
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if (origin < bound) { |
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int n = bound - origin, m = n - 1; |
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if ((n & m) == 0) |
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r = (r & m) + origin; |
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else if (n > 0) { |
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for (int u = r >>> 1; |
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u + m - (r = u % n) < 0; |
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u = mix32(nextSeed()) >>> 1) |
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; |
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r += origin; |
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} |
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else { |
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while (r < origin || r >= bound) |
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r = mix32(nextSeed()); |
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} |
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} |
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return r; |
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} |
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|
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/** |
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* The form of nextDouble used by DoubleStream Spliterators. |
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* |
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* @param origin the least value, unless greater than bound |
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* @param bound the upper bound (exclusive), must not equal origin |
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* @return a pseudorandom value |
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*/ |
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final double internalNextDouble(double origin, double bound) { |
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double r = (nextLong() >>> 11) * DOUBLE_UNIT; |
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if (origin < bound) { |
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r = r * (bound - origin) + origin; |
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if (r >= bound) // correct for rounding |
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r = Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1); |
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} |
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return r; |
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} |
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|
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/** |
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* Returns a pseudorandom {@code int} value. |
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* |
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* @return a pseudorandom {@code int} value |
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*/ |
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public int nextInt() { |
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return mix32(nextSeed()); |
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} |
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|
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/** |
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* Returns a pseudorandom {@code int} value between zero (inclusive) |
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* and the specified bound (exclusive). |
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* |
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* @param bound the bound on the random number to be returned. Must be |
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* positive. |
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* @return a pseudorandom {@code int} value between zero |
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* (inclusive) and the bound (exclusive) |
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* @throws IllegalArgumentException if {@code bound} is not positive |
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*/ |
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public int nextInt(int bound) { |
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if (bound <= 0) |
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throw new IllegalArgumentException(BadBound); |
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int r = mix32(nextSeed()); |
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int m = bound - 1; |
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if ((bound & m) == 0) // power of two |
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r &= m; |
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else { // reject over-represented candidates |
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for (int u = r >>> 1; |
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u + m - (r = u % bound) < 0; |
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u = mix32(nextSeed()) >>> 1) |
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; |
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} |
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return r; |
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} |
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|
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/** |
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* Returns a pseudorandom {@code int} value between the specified |
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* origin (inclusive) and the specified bound (exclusive). |
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* |
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* @param origin the least value returned |
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* @param bound the upper bound (exclusive) |
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* @return a pseudorandom {@code int} value between the origin |
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* (inclusive) and the bound (exclusive) |
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* @throws IllegalArgumentException if {@code origin} is greater than |
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* or equal to {@code bound} |
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*/ |
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public int nextInt(int origin, int bound) { |
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if (origin >= bound) |
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throw new IllegalArgumentException(BadRange); |
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return internalNextInt(origin, bound); |
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} |
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|
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/** |
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* Returns a pseudorandom {@code long} value. |
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* |
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* @return a pseudorandom {@code long} value |
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*/ |
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public long nextLong() { |
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return mix64(nextSeed()); |
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} |
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|
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/** |
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* Returns a pseudorandom {@code long} value between zero (inclusive) |
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* and the specified bound (exclusive). |
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* |
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* @param bound the bound on the random number to be returned. Must be |
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* positive. |
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* @return a pseudorandom {@code long} value between zero |
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* (inclusive) and the bound (exclusive) |
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* @throws IllegalArgumentException if {@code bound} is not positive |
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*/ |
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public long nextLong(long bound) { |
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if (bound <= 0) |
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throw new IllegalArgumentException(BadBound); |
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long r = mix64(nextSeed()); |
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long m = bound - 1; |
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if ((bound & m) == 0L) // power of two |
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r &= m; |
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else { // reject over-represented candidates |
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for (long u = r >>> 1; |
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u + m - (r = u % bound) < 0L; |
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u = mix64(nextSeed()) >>> 1) |
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; |
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} |
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return r; |
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} |
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|
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/** |
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* Returns a pseudorandom {@code long} value between the specified |
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* origin (inclusive) and the specified bound (exclusive). |
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* |
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* @param origin the least value returned |
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* @param bound the upper bound (exclusive) |
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* @return a pseudorandom {@code long} value between the origin |
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* (inclusive) and the bound (exclusive) |
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* @throws IllegalArgumentException if {@code origin} is greater than |
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* or equal to {@code bound} |
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*/ |
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public long nextLong(long origin, long bound) { |
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if (origin >= bound) |
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throw new IllegalArgumentException(BadRange); |
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return internalNextLong(origin, bound); |
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} |
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|
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/** |
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* Returns a pseudorandom {@code double} value between zero |
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* (inclusive) and one (exclusive). |
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* |
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* @return a pseudorandom {@code double} value between zero |
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* (inclusive) and one (exclusive) |
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*/ |
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public double nextDouble() { |
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return (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT; |
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} |
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|
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/** |
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* Returns a pseudorandom {@code double} value between 0.0 |
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* (inclusive) and the specified bound (exclusive). |
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* |
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* @param bound the bound on the random number to be returned. Must be |
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* positive. |
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* @return a pseudorandom {@code double} value between zero |
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* (inclusive) and the bound (exclusive) |
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* @throws IllegalArgumentException if {@code bound} is not positive |
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*/ |
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public double nextDouble(double bound) { |
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if (!(bound > 0.0)) |
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throw new IllegalArgumentException(BadBound); |
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double result = (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT * bound; |
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return (result < bound) ? result : // correct for rounding |
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Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1); |
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} |
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|
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/** |
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* Returns a pseudorandom {@code double} value between the specified |
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* origin (inclusive) and bound (exclusive). |
419 |
* |
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* @param origin the least value returned |
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* @param bound the upper bound |
422 |
* @return a pseudorandom {@code double} value between the origin |
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* (inclusive) and the bound (exclusive) |
424 |
* @throws IllegalArgumentException if {@code origin} is greater than |
425 |
* or equal to {@code bound} |
426 |
*/ |
427 |
public double nextDouble(double origin, double bound) { |
428 |
if (!(origin < bound)) |
429 |
throw new IllegalArgumentException(BadRange); |
430 |
return internalNextDouble(origin, bound); |
431 |
} |
432 |
|
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/** |
434 |
* Returns a pseudorandom {@code boolean} value. |
435 |
* |
436 |
* @return a pseudorandom {@code boolean} value |
437 |
*/ |
438 |
public boolean nextBoolean() { |
439 |
return mix32(nextSeed()) < 0; |
440 |
} |
441 |
|
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/** |
443 |
* Returns a pseudorandom {@code float} value between zero |
444 |
* (inclusive) and one (exclusive). |
445 |
* |
446 |
* @return a pseudorandom {@code float} value between zero |
447 |
* (inclusive) and one (exclusive) |
448 |
*/ |
449 |
public float nextFloat() { |
450 |
return (mix32(nextSeed()) >>> 8) * FLOAT_UNIT; |
451 |
} |
452 |
|
453 |
public double nextGaussian() { |
454 |
// Use nextLocalGaussian instead of nextGaussian field |
455 |
Double d = nextLocalGaussian.get(); |
456 |
if (d != null) { |
457 |
nextLocalGaussian.set(null); |
458 |
return d.doubleValue(); |
459 |
} |
460 |
double v1, v2, s; |
461 |
do { |
462 |
v1 = 2 * nextDouble() - 1; // between -1 and 1 |
463 |
v2 = 2 * nextDouble() - 1; // between -1 and 1 |
464 |
s = v1 * v1 + v2 * v2; |
465 |
} while (s >= 1 || s == 0); |
466 |
double multiplier = StrictMath.sqrt(-2 * StrictMath.log(s)/s); |
467 |
nextLocalGaussian.set(new Double(v2 * multiplier)); |
468 |
return v1 * multiplier; |
469 |
} |
470 |
|
471 |
@Override |
472 |
public DoubleStream gaussians() { |
473 |
return DoubleStream.generate(() -> current().nextGaussian()); |
474 |
} |
475 |
|
476 |
// stream methods, coded in a way intended to better isolate for |
477 |
// maintenance purposes the small differences across forms. |
478 |
|
479 |
/** |
480 |
* Returns a stream producing the given {@code streamSize} number of |
481 |
* pseudorandom {@code int} values. |
482 |
* |
483 |
* @param streamSize the number of values to generate |
484 |
* @return a stream of pseudorandom {@code int} values |
485 |
* @throws IllegalArgumentException if {@code streamSize} is |
486 |
* less than zero |
487 |
*/ |
488 |
public IntStream ints(long streamSize) { |
489 |
if (streamSize < 0L) |
490 |
throw new IllegalArgumentException(BadSize); |
491 |
return StreamSupport.intStream |
492 |
(new RandomIntsSpliterator |
493 |
(0L, streamSize, Integer.MAX_VALUE, 0), |
494 |
false); |
495 |
} |
496 |
|
497 |
/** |
498 |
* Returns an effectively unlimited stream of pseudorandom {@code int} |
499 |
* values. |
500 |
* |
501 |
* @implNote This method is implemented to be equivalent to {@code |
502 |
* ints(Long.MAX_VALUE)}. |
503 |
* |
504 |
* @return a stream of pseudorandom {@code int} values |
505 |
*/ |
506 |
public IntStream ints() { |
507 |
return StreamSupport.intStream |
508 |
(new RandomIntsSpliterator |
509 |
(0L, Long.MAX_VALUE, Integer.MAX_VALUE, 0), |
510 |
false); |
511 |
} |
512 |
|
513 |
/** |
514 |
* Returns a stream producing the given {@code streamSize} number of |
515 |
* pseudorandom {@code int} values, each conforming to the given |
516 |
* origin and bound. |
517 |
* |
518 |
* @param streamSize the number of values to generate |
519 |
* @param randomNumberOrigin the origin of each random value |
520 |
* @param randomNumberBound the bound of each random value |
521 |
* @return a stream of pseudorandom {@code int} values, |
522 |
* each with the given origin and bound |
523 |
* @throws IllegalArgumentException if {@code streamSize} is |
524 |
* less than zero, or {@code randomNumberOrigin} |
525 |
* is greater than or equal to {@code randomNumberBound} |
526 |
*/ |
527 |
public IntStream ints(long streamSize, int randomNumberOrigin, |
528 |
int randomNumberBound) { |
529 |
if (streamSize < 0L) |
530 |
throw new IllegalArgumentException(BadSize); |
531 |
if (randomNumberOrigin >= randomNumberBound) |
532 |
throw new IllegalArgumentException(BadRange); |
533 |
return StreamSupport.intStream |
534 |
(new RandomIntsSpliterator |
535 |
(0L, streamSize, randomNumberOrigin, randomNumberBound), |
536 |
false); |
537 |
} |
538 |
|
539 |
/** |
540 |
* Returns an effectively unlimited stream of pseudorandom {@code |
541 |
* int} values, each conforming to the given origin and bound. |
542 |
* |
543 |
* @implNote This method is implemented to be equivalent to {@code |
544 |
* ints(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}. |
545 |
* |
546 |
* @param randomNumberOrigin the origin of each random value |
547 |
* @param randomNumberBound the bound of each random value |
548 |
* @return a stream of pseudorandom {@code int} values, |
549 |
* each with the given origin and bound |
550 |
* @throws IllegalArgumentException if {@code randomNumberOrigin} |
551 |
* is greater than or equal to {@code randomNumberBound} |
552 |
*/ |
553 |
public IntStream ints(int randomNumberOrigin, int randomNumberBound) { |
554 |
if (randomNumberOrigin >= randomNumberBound) |
555 |
throw new IllegalArgumentException(BadRange); |
556 |
return StreamSupport.intStream |
557 |
(new RandomIntsSpliterator |
558 |
(0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound), |
559 |
false); |
560 |
} |
561 |
|
562 |
/** |
563 |
* Returns a stream producing the given {@code streamSize} number of |
564 |
* pseudorandom {@code long} values. |
565 |
* |
566 |
* @param streamSize the number of values to generate |
567 |
* @return a stream of pseudorandom {@code long} values |
568 |
* @throws IllegalArgumentException if {@code streamSize} is |
569 |
* less than zero |
570 |
*/ |
571 |
public LongStream longs(long streamSize) { |
572 |
if (streamSize < 0L) |
573 |
throw new IllegalArgumentException(BadSize); |
574 |
return StreamSupport.longStream |
575 |
(new RandomLongsSpliterator |
576 |
(0L, streamSize, Long.MAX_VALUE, 0L), |
577 |
false); |
578 |
} |
579 |
|
580 |
/** |
581 |
* Returns an effectively unlimited stream of pseudorandom {@code long} |
582 |
* values. |
583 |
* |
584 |
* @implNote This method is implemented to be equivalent to {@code |
585 |
* longs(Long.MAX_VALUE)}. |
586 |
* |
587 |
* @return a stream of pseudorandom {@code long} values |
588 |
*/ |
589 |
public LongStream longs() { |
590 |
return StreamSupport.longStream |
591 |
(new RandomLongsSpliterator |
592 |
(0L, Long.MAX_VALUE, Long.MAX_VALUE, 0L), |
593 |
false); |
594 |
} |
595 |
|
596 |
/** |
597 |
* Returns a stream producing the given {@code streamSize} number of |
598 |
* pseudorandom {@code long} values, each conforming to the |
599 |
* given origin and bound. |
600 |
* |
601 |
* @param streamSize the number of values to generate |
602 |
* @param randomNumberOrigin the origin of each random value |
603 |
* @param randomNumberBound the bound of each random value |
604 |
* @return a stream of pseudorandom {@code long} values, |
605 |
* each with the given origin and bound |
606 |
* @throws IllegalArgumentException if {@code streamSize} is |
607 |
* less than zero, or {@code randomNumberOrigin} |
608 |
* is greater than or equal to {@code randomNumberBound} |
609 |
*/ |
610 |
public LongStream longs(long streamSize, long randomNumberOrigin, |
611 |
long randomNumberBound) { |
612 |
if (streamSize < 0L) |
613 |
throw new IllegalArgumentException(BadSize); |
614 |
if (randomNumberOrigin >= randomNumberBound) |
615 |
throw new IllegalArgumentException(BadRange); |
616 |
return StreamSupport.longStream |
617 |
(new RandomLongsSpliterator |
618 |
(0L, streamSize, randomNumberOrigin, randomNumberBound), |
619 |
false); |
620 |
} |
621 |
|
622 |
/** |
623 |
* Returns an effectively unlimited stream of pseudorandom {@code |
624 |
* long} values, each conforming to the given origin and bound. |
625 |
* |
626 |
* @implNote This method is implemented to be equivalent to {@code |
627 |
* longs(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}. |
628 |
* |
629 |
* @param randomNumberOrigin the origin of each random value |
630 |
* @param randomNumberBound the bound of each random value |
631 |
* @return a stream of pseudorandom {@code long} values, |
632 |
* each with the given origin and bound |
633 |
* @throws IllegalArgumentException if {@code randomNumberOrigin} |
634 |
* is greater than or equal to {@code randomNumberBound} |
635 |
*/ |
636 |
public LongStream longs(long randomNumberOrigin, long randomNumberBound) { |
637 |
if (randomNumberOrigin >= randomNumberBound) |
638 |
throw new IllegalArgumentException(BadRange); |
639 |
return StreamSupport.longStream |
640 |
(new RandomLongsSpliterator |
641 |
(0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound), |
642 |
false); |
643 |
} |
644 |
|
645 |
/** |
646 |
* Returns a stream producing the given {@code streamSize} number of |
647 |
* pseudorandom {@code double} values, each between zero |
648 |
* (inclusive) and one (exclusive). |
649 |
* |
650 |
* @param streamSize the number of values to generate |
651 |
* @return a stream of {@code double} values |
652 |
* @throws IllegalArgumentException if {@code streamSize} is |
653 |
* less than zero |
654 |
*/ |
655 |
public DoubleStream doubles(long streamSize) { |
656 |
if (streamSize < 0L) |
657 |
throw new IllegalArgumentException(BadSize); |
658 |
return StreamSupport.doubleStream |
659 |
(new RandomDoublesSpliterator |
660 |
(0L, streamSize, Double.MAX_VALUE, 0.0), |
661 |
false); |
662 |
} |
663 |
|
664 |
/** |
665 |
* Returns an effectively unlimited stream of pseudorandom {@code |
666 |
* double} values, each between zero (inclusive) and one |
667 |
* (exclusive). |
668 |
* |
669 |
* @implNote This method is implemented to be equivalent to {@code |
670 |
* doubles(Long.MAX_VALUE)}. |
671 |
* |
672 |
* @return a stream of pseudorandom {@code double} values |
673 |
*/ |
674 |
public DoubleStream doubles() { |
675 |
return StreamSupport.doubleStream |
676 |
(new RandomDoublesSpliterator |
677 |
(0L, Long.MAX_VALUE, Double.MAX_VALUE, 0.0), |
678 |
false); |
679 |
} |
680 |
|
681 |
/** |
682 |
* Returns a stream producing the given {@code streamSize} number of |
683 |
* pseudorandom {@code double} values, each conforming to the |
684 |
* given origin and bound. |
685 |
* |
686 |
* @param streamSize the number of values to generate |
687 |
* @param randomNumberOrigin the origin of each random value |
688 |
* @param randomNumberBound the bound of each random value |
689 |
* @return a stream of pseudorandom {@code double} values, |
690 |
* each with the given origin and bound |
691 |
* @throws IllegalArgumentException if {@code streamSize} is |
692 |
* less than zero |
693 |
* @throws IllegalArgumentException if {@code randomNumberOrigin} |
694 |
* is greater than or equal to {@code randomNumberBound} |
695 |
*/ |
696 |
public DoubleStream doubles(long streamSize, double randomNumberOrigin, |
697 |
double randomNumberBound) { |
698 |
if (streamSize < 0L) |
699 |
throw new IllegalArgumentException(BadSize); |
700 |
if (!(randomNumberOrigin < randomNumberBound)) |
701 |
throw new IllegalArgumentException(BadRange); |
702 |
return StreamSupport.doubleStream |
703 |
(new RandomDoublesSpliterator |
704 |
(0L, streamSize, randomNumberOrigin, randomNumberBound), |
705 |
false); |
706 |
} |
707 |
|
708 |
/** |
709 |
* Returns an effectively unlimited stream of pseudorandom {@code |
710 |
* double} values, each conforming to the given origin and bound. |
711 |
* |
712 |
* @implNote This method is implemented to be equivalent to {@code |
713 |
* doubles(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}. |
714 |
* |
715 |
* @param randomNumberOrigin the origin of each random value |
716 |
* @param randomNumberBound the bound of each random value |
717 |
* @return a stream of pseudorandom {@code double} values, |
718 |
* each with the given origin and bound |
719 |
* @throws IllegalArgumentException if {@code randomNumberOrigin} |
720 |
* is greater than or equal to {@code randomNumberBound} |
721 |
*/ |
722 |
public DoubleStream doubles(double randomNumberOrigin, double randomNumberBound) { |
723 |
if (!(randomNumberOrigin < randomNumberBound)) |
724 |
throw new IllegalArgumentException(BadRange); |
725 |
return StreamSupport.doubleStream |
726 |
(new RandomDoublesSpliterator |
727 |
(0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound), |
728 |
false); |
729 |
} |
730 |
|
731 |
/** |
732 |
* Spliterator for int streams. We multiplex the four int |
733 |
* versions into one class by treating a bound less than origin as |
734 |
* unbounded, and also by treating "infinite" as equivalent to |
735 |
* Long.MAX_VALUE. For splits, it uses the standard divide-by-two |
736 |
* approach. The long and double versions of this class are |
737 |
* identical except for types. |
738 |
*/ |
739 |
static final class RandomIntsSpliterator implements Spliterator.OfInt { |
740 |
long index; |
741 |
final long fence; |
742 |
final int origin; |
743 |
final int bound; |
744 |
RandomIntsSpliterator(long index, long fence, |
745 |
int origin, int bound) { |
746 |
this.index = index; this.fence = fence; |
747 |
this.origin = origin; this.bound = bound; |
748 |
} |
749 |
|
750 |
public RandomIntsSpliterator trySplit() { |
751 |
long i = index, m = (i + fence) >>> 1; |
752 |
return (m <= i) ? null : |
753 |
new RandomIntsSpliterator(i, index = m, origin, bound); |
754 |
} |
755 |
|
756 |
public long estimateSize() { |
757 |
return fence - index; |
758 |
} |
759 |
|
760 |
public int characteristics() { |
761 |
return (Spliterator.SIZED | Spliterator.SUBSIZED | |
762 |
Spliterator.NONNULL | Spliterator.IMMUTABLE); |
763 |
} |
764 |
|
765 |
public boolean tryAdvance(IntConsumer consumer) { |
766 |
if (consumer == null) throw new NullPointerException(); |
767 |
long i = index, f = fence; |
768 |
if (i < f) { |
769 |
consumer.accept(ThreadLocalRandom.current().internalNextInt(origin, bound)); |
770 |
index = i + 1; |
771 |
return true; |
772 |
} |
773 |
return false; |
774 |
} |
775 |
|
776 |
public void forEachRemaining(IntConsumer consumer) { |
777 |
if (consumer == null) throw new NullPointerException(); |
778 |
long i = index, f = fence; |
779 |
if (i < f) { |
780 |
index = f; |
781 |
int o = origin, b = bound; |
782 |
ThreadLocalRandom rng = ThreadLocalRandom.current(); |
783 |
do { |
784 |
consumer.accept(rng.internalNextInt(o, b)); |
785 |
} while (++i < f); |
786 |
} |
787 |
} |
788 |
} |
789 |
|
790 |
/** |
791 |
* Spliterator for long streams. |
792 |
*/ |
793 |
static final class RandomLongsSpliterator implements Spliterator.OfLong { |
794 |
long index; |
795 |
final long fence; |
796 |
final long origin; |
797 |
final long bound; |
798 |
RandomLongsSpliterator(long index, long fence, |
799 |
long origin, long bound) { |
800 |
this.index = index; this.fence = fence; |
801 |
this.origin = origin; this.bound = bound; |
802 |
} |
803 |
|
804 |
public RandomLongsSpliterator trySplit() { |
805 |
long i = index, m = (i + fence) >>> 1; |
806 |
return (m <= i) ? null : |
807 |
new RandomLongsSpliterator(i, index = m, origin, bound); |
808 |
} |
809 |
|
810 |
public long estimateSize() { |
811 |
return fence - index; |
812 |
} |
813 |
|
814 |
public int characteristics() { |
815 |
return (Spliterator.SIZED | Spliterator.SUBSIZED | |
816 |
Spliterator.NONNULL | Spliterator.IMMUTABLE); |
817 |
} |
818 |
|
819 |
public boolean tryAdvance(LongConsumer consumer) { |
820 |
if (consumer == null) throw new NullPointerException(); |
821 |
long i = index, f = fence; |
822 |
if (i < f) { |
823 |
consumer.accept(ThreadLocalRandom.current().internalNextLong(origin, bound)); |
824 |
index = i + 1; |
825 |
return true; |
826 |
} |
827 |
return false; |
828 |
} |
829 |
|
830 |
public void forEachRemaining(LongConsumer consumer) { |
831 |
if (consumer == null) throw new NullPointerException(); |
832 |
long i = index, f = fence; |
833 |
if (i < f) { |
834 |
index = f; |
835 |
long o = origin, b = bound; |
836 |
ThreadLocalRandom rng = ThreadLocalRandom.current(); |
837 |
do { |
838 |
consumer.accept(rng.internalNextLong(o, b)); |
839 |
} while (++i < f); |
840 |
} |
841 |
} |
842 |
|
843 |
} |
844 |
|
845 |
/** |
846 |
* Spliterator for double streams. |
847 |
*/ |
848 |
static final class RandomDoublesSpliterator implements Spliterator.OfDouble { |
849 |
long index; |
850 |
final long fence; |
851 |
final double origin; |
852 |
final double bound; |
853 |
RandomDoublesSpliterator(long index, long fence, |
854 |
double origin, double bound) { |
855 |
this.index = index; this.fence = fence; |
856 |
this.origin = origin; this.bound = bound; |
857 |
} |
858 |
|
859 |
public RandomDoublesSpliterator trySplit() { |
860 |
long i = index, m = (i + fence) >>> 1; |
861 |
return (m <= i) ? null : |
862 |
new RandomDoublesSpliterator(i, index = m, origin, bound); |
863 |
} |
864 |
|
865 |
public long estimateSize() { |
866 |
return fence - index; |
867 |
} |
868 |
|
869 |
public int characteristics() { |
870 |
return (Spliterator.SIZED | Spliterator.SUBSIZED | |
871 |
Spliterator.NONNULL | Spliterator.IMMUTABLE); |
872 |
} |
873 |
|
874 |
public boolean tryAdvance(DoubleConsumer consumer) { |
875 |
if (consumer == null) throw new NullPointerException(); |
876 |
long i = index, f = fence; |
877 |
if (i < f) { |
878 |
consumer.accept(ThreadLocalRandom.current().internalNextDouble(origin, bound)); |
879 |
index = i + 1; |
880 |
return true; |
881 |
} |
882 |
return false; |
883 |
} |
884 |
|
885 |
public void forEachRemaining(DoubleConsumer consumer) { |
886 |
if (consumer == null) throw new NullPointerException(); |
887 |
long i = index, f = fence; |
888 |
if (i < f) { |
889 |
index = f; |
890 |
double o = origin, b = bound; |
891 |
ThreadLocalRandom rng = ThreadLocalRandom.current(); |
892 |
do { |
893 |
consumer.accept(rng.internalNextDouble(o, b)); |
894 |
} while (++i < f); |
895 |
} |
896 |
} |
897 |
} |
898 |
|
899 |
|
900 |
// Within-package utilities |
901 |
|
902 |
/* |
903 |
* Descriptions of the usages of the methods below can be found in |
904 |
* the classes that use them. Briefly, a thread's "probe" value is |
905 |
* a non-zero hash code that (probably) does not collide with |
906 |
* other existing threads with respect to any power of two |
907 |
* collision space. When it does collide, it is pseudo-randomly |
908 |
* adjusted (using a Marsaglia XorShift). The nextSecondarySeed |
909 |
* method is used in the same contexts as ThreadLocalRandom, but |
910 |
* only for transient usages such as random adaptive spin/block |
911 |
* sequences for which a cheap RNG suffices and for which it could |
912 |
* in principle disrupt user-visible statistical properties of the |
913 |
* main ThreadLocalRandom if we were to use it. |
914 |
* |
915 |
* Note: Because of package-protection issues, versions of some |
916 |
* these methods also appear in some subpackage classes. |
917 |
*/ |
918 |
|
919 |
/** |
920 |
* Returns the probe value for the current thread without forcing |
921 |
* initialization. Note that invoking ThreadLocalRandom.current() |
922 |
* can be used to force initialization on zero return. |
923 |
*/ |
924 |
static final int getProbe() { |
925 |
return UNSAFE.getInt(Thread.currentThread(), PROBE); |
926 |
} |
927 |
|
928 |
/** |
929 |
* Pseudo-randomly advances and records the given probe value for the |
930 |
* given thread. |
931 |
*/ |
932 |
static final int advanceProbe(int probe) { |
933 |
probe ^= probe << 13; // xorshift |
934 |
probe ^= probe >>> 17; |
935 |
probe ^= probe << 5; |
936 |
UNSAFE.putInt(Thread.currentThread(), PROBE, probe); |
937 |
return probe; |
938 |
} |
939 |
|
940 |
/** |
941 |
* Returns the pseudo-randomly initialized or updated secondary seed. |
942 |
*/ |
943 |
static final int nextSecondarySeed() { |
944 |
int r; |
945 |
Thread t = Thread.currentThread(); |
946 |
if ((r = UNSAFE.getInt(t, SECONDARY)) != 0) { |
947 |
r ^= r << 13; // xorshift |
948 |
r ^= r >>> 17; |
949 |
r ^= r << 5; |
950 |
} |
951 |
else { |
952 |
localInit(); |
953 |
if ((r = (int)UNSAFE.getLong(t, SEED)) == 0) |
954 |
r = 1; // avoid zero |
955 |
} |
956 |
UNSAFE.putInt(t, SECONDARY, r); |
957 |
return r; |
958 |
} |
959 |
|
960 |
// Serialization support |
961 |
|
962 |
private static final long serialVersionUID = -5851777807851030925L; |
963 |
|
964 |
/** |
965 |
* @serialField rnd long |
966 |
* seed for random computations |
967 |
* @serialField initialized boolean |
968 |
* always true |
969 |
*/ |
970 |
private static final ObjectStreamField[] serialPersistentFields = { |
971 |
new ObjectStreamField("rnd", long.class), |
972 |
new ObjectStreamField("initialized", boolean.class), |
973 |
}; |
974 |
|
975 |
/** |
976 |
* Saves the {@code ThreadLocalRandom} to a stream (that is, serializes it). |
977 |
* @param s the stream |
978 |
* @throws java.io.IOException if an I/O error occurs |
979 |
*/ |
980 |
private void writeObject(java.io.ObjectOutputStream s) |
981 |
throws java.io.IOException { |
982 |
|
983 |
java.io.ObjectOutputStream.PutField fields = s.putFields(); |
984 |
fields.put("rnd", UNSAFE.getLong(Thread.currentThread(), SEED)); |
985 |
fields.put("initialized", true); |
986 |
s.writeFields(); |
987 |
} |
988 |
|
989 |
/** |
990 |
* Returns the {@link #current() current} thread's {@code ThreadLocalRandom}. |
991 |
* @return the {@link #current() current} thread's {@code ThreadLocalRandom} |
992 |
*/ |
993 |
private Object readResolve() { |
994 |
return current(); |
995 |
} |
996 |
|
997 |
// Unsafe mechanics |
998 |
private static final sun.misc.Unsafe UNSAFE; |
999 |
private static final long SEED; |
1000 |
private static final long PROBE; |
1001 |
private static final long SECONDARY; |
1002 |
static { |
1003 |
try { |
1004 |
UNSAFE = sun.misc.Unsafe.getUnsafe(); |
1005 |
Class<?> tk = Thread.class; |
1006 |
SEED = UNSAFE.objectFieldOffset |
1007 |
(tk.getDeclaredField("threadLocalRandomSeed")); |
1008 |
PROBE = UNSAFE.objectFieldOffset |
1009 |
(tk.getDeclaredField("threadLocalRandomProbe")); |
1010 |
SECONDARY = UNSAFE.objectFieldOffset |
1011 |
(tk.getDeclaredField("threadLocalRandomSecondarySeed")); |
1012 |
} catch (Exception e) { |
1013 |
throw new Error(e); |
1014 |
} |
1015 |
} |
1016 |
} |